I am familiar with the theory on generating the positions of the members of the solar system, but have been unable to find out the standard practices and methods of professional astronomers in acquiring this information. The basic methods of generating an ephemeris of the solar system can be found on the Wikipedia. Also, I have the book Astronomical Algorithms by Jean Meeus.

How do practicing astronomers do it though? Are there standard programs or software that everyone uses, or do they access servers at some international body that returns positions at a given time, or does each astronomer have his own custom program that he made? What is the normal way an astronomer gets planetary positions?


There are a number of different organizations that produce ephemeris models of the solar system. Even within one organization, there a number of different ephemeris models.

The three leading organizations that produce solar system ephemerides are

  • The Jet Propulsion Laboratory (JPL) in the USA, which produces the Development Ephemeris (DE) series of solar system ephemerides (and also ephemerides for many of the smaller bodies in the solar system);

  • The Institute of Applied Astronomy at the Russian Academy of Sciences, which produces the Ephemerides of the Planets and Moon (EPM) series of solar system ephemerides; and

  • The Institut de Mecanique Celeste et de Calcul de Ephemerides (IMCCE) in France, which produces the INPOP series of solar system ephemerides.

There appears to exist a friendly spirit of competition and cooperation amongst these three groups. They apparently share measurements and ideas amongst one another. They do not exactly agree on results (which is a good thing). Each group regularly updates their respective ephemeris models as new measurements are gathered, and as numerical integration techniques and computing capabilities are improved.


I have found the answer to this question. Most people use the Jet Propulsion Laboratory Development Ephemeris or JPL-DE as it is known. The book Explanatory Supplement to the Astronomical Almanac explains the methods of the JPL-DE and how to use it.

  • $\begingroup$ -1. This answer is fundamentally wrong. Everybody does not use the same ephemeris. There are multiple versions of the JPL Development Ephemeris, and other organizations develop ephemerides that compete with the JPL ephemerides. $\endgroup$ – David Hammen Nov 22 '14 at 15:21
  • $\begingroup$ A JPL Development Ephemeris describes the positions of the Sun, the eight planets, Pluto, and the Moon. Some also describe the Earth's rotation axis and the orientation of the Moon. You need a different ephemeris if you are interested in asteroids, stars, or galaxies. $\endgroup$ – David Hammen Nov 22 '14 at 15:36

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